Fiber-containing cutting tools

ABSTRACT

Fibers for diamond-impregnated cutting tools and their associated methods for manufacture and use are described. A matrix is formed that contains fibers made from carbon, glass, ceramic, polymer, and the like. The matrix is then sintered to form a cutting portion of a drill bit. The type and concentration of the fibers can be modified to control the tensile strength and the erosion rate of the matrix to optimize the cutting performance of the tools. Additionally, the fibers may be added to the cutting section to weaken the structure and allow higher modulus binders to be used for the cutting tools at a lower cost, allowing the amount of fibers to be tailored to retain the diamonds in the cutting portion for the desired amount. As the cutting portion erodes, the fibers may also increase the lubricity at the face of the cutting portion.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is a divisional application of U.S. patentapplication Ser. No. 11/948,185, filed on Nov. 30, 2007, entitled“Fiber-Containing Diamond-Impregnated Cutting Tools,” which claimspriority to and the benefit of U.S. Provisional Application Ser. No.60/917,016, filed May 9, 2007, entitled “Fiber-Reinforced Diamond Wire,”and U.S. Provisional Application Ser. No. 60/867,882, filed Nov. 30,2006, entitled “Fiber-Reinforced Core Drill Bit.” The contents of eachof the above-referenced applications are hereby incorporated byreference in their entirety.

BACKGROUND OF THE INVENTION

1. The Field of the Invention

This application relates generally to cutting tools and their methods ofuse. In particular, this application relates to diamond-impregnatedcutting tools that may contain fibers.

2. Discussion of the Relevant Art

Cutting tools can be impregnated with diamonds so that they can be usedto grind, polish, or otherwise cut a variety of materials that normalcutting tools cannot. The part of these tools that performs the cuttingaction (or the cutting portion of the tool) is generally formed of amatrix that contains a powdered metal or a hard particulate material,such as tungsten carbide. This material is sometimes infiltrated with abinder, such as a copper alloy. Finally, the cutting portion of thesetools is impregnated with diamond crystals or some other form ofabrasive cutting media. As the tool grinds and cuts the desiredmaterials, the cutting portion of the tool erodes and exposes new layersof the diamond crystal (or other cutting media) so that a sharp surfaceis always available for the cutting process. Any diamond-impregnatedcutting tool may continue to cut efficiently until the diamondimpregnated portion of the tool is completely consumed. At that point,the tool becomes dull and must be replaced with another one.

In some cases, diamond-impregnated cutting tools may be expensive andtheir replacement may be time consuming, costly, as well as dangerous.For example, the replacement of a diamond-impregnated core samplingdrill bit requires removing (or tripping out) the entire drill stringout of the hole that has been drilled (the borehole). Each section ofthe drill rod must be sequentially removed from the borehole. Once thedrill bit is replaced, the entire drill string must be assembled sectionby section and then tripped back into the borehole. Depending on thedepth of the hole and the characteristics of the materials beingdrilled, this process may need to be repeated multiple times for asingle borehole.

As well, conventional diamond-impregnated cutting tools often haveseveral characteristics that can add to the consumption rate of thecutting portion and, therefore, increase the operating costs associatedwith those cutting tools. First, the binder materials in the tools maybe relatively soft in comparison to the cutting media. Accordingly, thecutting portion may erode and allow diamonds or other abrasive cuttingmaterials to slough off prematurely. Second, the erosion rate of thecutting portion can be increased by insufficient lubrication to andaround the cutting face of the tool, or the interface between thecutting portion of the tool and the material being cut. Third,conventional impregnated cutting tools may also be too wear resistant toexpose and renew layers of the cutting portion.

BRIEF SUMMARY OF THE INVENTION

This application describes diamond-impregnated cutting tools and theirassociated methods for manufacture and use. The cutting tools contain adiamond-impregnated cutting portion that may contain fibers made fromcarbon, glass, ceramic, polymer, and the like. The fibers can be in anyform, including chopped and milled fibers. The fibers may also be coatedwith metal, ceramic, or other performance-enhancing coatings. The fibersmay be used to both control the tensile strength control the erosionrate of the matrix in the cutting portion to optimize the cuttingperformance of the tools. Additionally, the fibers may also weaken thestructure and allow higher modulus binders to be used for the cuttingtools at a lower cost, allowing the amount of fibers to be tailored toretain the diamonds in the cutting portion for the desired amount oftime. And as the cutting portion erodes, the fibers may also increasethe lubricity at the face of the cutting portion. Using the fibersallows the cutting tools to last longer and make them safer and moreeconomical because they need to be replaced less often.

BRIEF DESCRIPTION OF THE DRAWINGS

The following description can be better understood in light of theFigures, in which:

FIG. 1 contains an exemplary view of a core sampling drill bit;

FIG. 2 contains an exemplary view of a cross section of a diamond wire;

FIG. 3 contains an exemplary view of a cross section of another diamondwire; and

FIG. 4 contains an exemplary view of a cross section of an individualdiamond wire bead.

Together with the following description, the Figures may helpdemonstrate and explain the principles of the invention and methods forusing the invention. In the Figures, the thickness and configuration ofcomponents may be exaggerated for clarity. The same reference numeralsin different Figures represent the same component.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description supplies specific details in order to providea thorough understanding. Nevertheless, the skilled artisan wouldunderstand that the apparatus and associated methods of making and usingthe apparatus can be implemented and used without employing thesespecific details. Indeed, the apparatus and associated methods can beused in conjunction with any systems, components, and/or techniquesconventionally used in the industry. For example, while the descriptionbelow focuses on using fibers in diamond-impregnated cutting tools, thisinvention may be implemented in many other cutting tool applications,such as in cutting tools that are impregnated with any cutting medialike super-abrasive materials (e.g., polycrystalline diamond), aluminumoxide, silicon carbide, silicon nitride, tungsten carbide, cubic boronnitride, alumina, seeded or unseeded sol-gel alumina, etc., andcombinations thereof.

The cutting tools described herein can be used to cut stone,subterranean mineral formations, ceramics, asphalt, concrete, and otherhard materials. These cutting tools may include core sampling drillbits, drag-type drill bits, roller cone drill bits, diamond wire,grinding cups, diamond blades, tuck pointers, crack chasers, and thelike. For example, the cutting tools may be any type of earth drill bit(i.e., core sampling drill bit, drag drill bit, roller cone bit,navi-drill, full hole drill, hole saw, hole opener, etc.), diamond sawblade (e.g., laser welded blade, concave diamond blade, segmented blade,continuous rim blade, wavy core blade, ventilated core blade, etc.),grinding cup (e.g., single row cup, double row cup, grinding cup withT-shaped segments, etc.), tuck pointer (e.g., triple row, etc.), crackchaser, polishing disk, and so forth. In some embodiments, though, thecutting tools are core sampling drill bits and diamond wire.

The part of the cutting tools that performs the cutting action (or thecutting portion of the tool) contains a matrix with a powdered metal ora hard particulate material, such as tungsten carbide or any othersuper-abrasive material. This material can sometimes be infiltrated witha binder, such as a copper alloy or a substantial equivalent, and can besintered to form a segment. The cutting portion of these tools can alsobe impregnated with diamonds, or some other form of abrasive cuttingmedia, and mixed (and, in some embodiments, reinforced) with fibrousmaterials (or fibers) as described in detail in the embodiments wherethe cutting tool is a core sampling drill bit and a diamond wire.

FIG. 1 illustrates one example of a fiber-containing cutting tool, afiber-containing (and, in some embodiments, fiber-reinforced) coresampling drill bit. As shown in FIG. 1, the drill bit 20 contains afirst section 21 that connects to the rest of the drill string. Thedrill bit 20 also contains a second section 22 that is used to cut thedesired materials during the drilling process. The body of the drill bit20 has an outer surface and an inner surface containing a hollow portiontherein. With this configuration, pieces of the material being drilledcan pass through the hollow portion, up into a drill string to which thedrill bit is connected, and then be collected.

The drill bit 20 may be any size, and may therefore be used to collectcore samples of any size. While the drill bit may have any circumferenceand may be used to remove and collect core samples with any desireddiameter, the diameter generally ranges from about 1 to about 12 inches.As well, while the kerf of the drill bit (the radius of the outersurface minus the radius of the inner surface) may be any width, itgenerally ranges from about ½ of an inch to about 6 inches.

The first section 21 of the drill bit may be made of any suitablematerial known in the art. In some embodiments, the first section may bemade of steel or a matrix casting of a hard particulate material in abinder. In some embodiments, the first section 21 may contain a chuckend, sometimes called a blank, bit body, or shank, that may be used forany purpose, including connecting the drill bit to the nearest part ofthe drill string. Thus, the chuck end can be configured as known in theart to connect the drill bit 20 to any desired part of the drill string.

The second section 22 of the core sampling drill bit 20 contains acutting portion with cutting elements 12 having a cutting face 14. Thecutting elements 12 have a space 16 between them so that, as known inthe art, a drilling fluid following the path shown by the arrow may beused during drilling. The cutting portion of the core sampling drillbit, often called the crown, may be constructed of any material(s) knownin the art. This type of drill bit (a core sampling bit) is generallyformed of steel or a matrix of powdered metal, which is a hardparticulate material, such as tungsten carbide, tungsten, iron, cobalt,and/or molybdenum. This material may then be infiltrated with a binder,such as a copper alloy, zinc, silver, molybdenum, nickel, cobalt, or asubstantial equivalent, and/or may be sintered. The cutting portion ofthe drill bit may also be impregnated with any form or combination offorms of cutting media, such as diamond crystals.

The cutting media used in the drill bit may have any desiredcharacteristic or combination of characteristics. For instance, thecutting media may be of any size, shape, grain, quality, grit,concentration, etc. In some embodiments, the cutting media may be verysmall and substantially round in order to leave a smooth finish on thematerial being cut by the core sampling drill bit. In other embodiments,the cutting media may be larger to cut aggressively into the materialbeing cut.

The cutting media may be contained homogeneously or heterogeneously inthe drill bit. As well, the cutting media may be aligned in a particularmanner so that the cutting properties of the media are presented in anadvantageous position with respect to the cutting portion of the drillbit. Similarly, the cutting media may be contained in the drill bit in avariety of densities as desired for a particular use. For example, largeabrasive particles spaced further apart may cut material more quicklythan small abrasive particles packed tightly together. But the size,density, and shape of the abrasive particles may be provided in avariety of combinations depending on desired cost and performance of thedrill bit.

In some instances, the cutting portion of the drill bit may be made ofone or more layers. For example, the cutting portion may contain twolayers: a matrix layer that performs the cutting operation and a backinglayer, which connects the matrix layer to the first section of the drillbit. In these embodiments, the matrix layer contains the actual cuttingmedia that abrades and erodes the material being drilled. The portion ofthe matrix layer that comes in contact with the material being cut isknown as the cutting face.

Another embodiment of a cutting tool comprises a fiber-containing (and,in some embodiments, a fiber-reinforced) diamond wire segments or beads.Diamond wire may be used to cut a variety of hard materials. Forexample, a relatively large diamond wire may be used to cut large blocksof granite out of a granite formation in a quarry for furtherprocessing. However, in other uses, a relatively small diamond wire maybe used in a laboratory to cut a sample of a hard material for testing.

One example a diamond wire is shown in FIG. 2. In FIG. 2, the diamondwires contain a core wire 2 made of any suitable strong material, suchas steel, that may be coated with a cutting material coating 4. Thecoating 4 in such wires may act as the cutting portion of the diamondwire. The coating 4 may contain a binder (e.g., a copper alloy, iron,silicon carbide, etc.) and a base material that may be formed from steelor a matrix of powdered metal/hard particulate material (e.g., tungstencarbide, tungsten, iron, cobalt, molybdenum, etc.). The coating 4 mayalso be impregnated with any cutting media 8, such as diamond crystals.The cutting media 8 in the coating 4 may have any desiredcharacteristic, including any size, shape, alignment, grain, quality,grit, concentration, disbursement, and so forth.

In some instances, the coating 4 of the diamond wire may be made of oneor more layers. In such embodiments, each layer may be made of anydesired material. For example, the backing layer may contain an ironalloy and the bond between the matrix and backing layer is usuallyachieved with a copper alloy or braze alloy.

FIG. 3 illustrates another example of a fiber-containing diamond wire.As shown in FIG. 3, the diamond wires may have abrasive beads that areapplied to a core cable 28 (or core wire) to create a continuous stringof abrasive beads that act as cutting portions on the diamond wire. Theabrasive beads may be formed from any suitable material. For example,the abrasive beads may have a diamond matrix 27 formed of a basematerial, like powdered metal or a hard particulate material (e.g.,tungsten carbide, tungsten, cobalt, molybdenum, etc.). The base materialmay be infiltrated with a binding material (e.g., a copper alloy). Andthe abrasive beads may be impregnated with any cutting media (e.g.,diamond crystals) having any desired characteristic, including any size,shape, alignment, grain, quality, grit, concentration, disbursement, andthe like.

FIG. 4 illustrates an individual diamond wire bead 26 that is used withthe diamond wire shown in FIG. 3. The bead 26 may be of any shape andsize known in the art and may be applied to the core wire in any mannerknown in the art. The diamond wire in FIG. 3, for example, may be madeby manufacturing the bead 26 to contain a coating 34 with abrasiveparticles 38 and fibers 36 and a channel 32. In this example, the bead26 may then be attached to a steel ferrule, which may be threaded ontothe core wire. Therefore, the beads 26 on the diamond wire may bemanufactured separately from the core wire and then strung on the corewire with other beads to create the diamond wire. An encapsulant,usually a rubber 25 or some other polymeric material, can be coated onthe core wire between the beads as known in the art to create thediamond wire.

The diamond wires may also be any size and may therefore be used in anyknown process using diamond wire. For example, the diamond wire in FIG.3 may range in length from about 5 meters to more than 100 meters andhave beads 26 with a diameter of from about 4 millimeters to about 12millimeters. And for the diamond wire in FIG. 2, the length can be about10 centimeters long and the diameter of the core wire and cuttingmaterial coating can be about a few microns. Nevertheless, the diamondwire can be longer or shorter than the lengths in the previous examplesand may also have beads and a cable of any desired diameter.

In addition to these features, the diamond-impregnated cuttingtools-including the core sampling drill bits or diamond wires-may haveany additional feature known in the art. For example, a core samplingdrill bit may have additional gauge protection, hard-strip deposits,various bit profiles, and combinations thereof. Protector gauges on orin a drill bit may be included to reduce the damage to the drill bit andwell casing as the drill bit is lowered into the casing. Additionally,the core sampling drill bit may have hard-metal strips applied that mayprevent the premature erosion of the cutting portion of the drill bit.

The cutting portion(s) of the diamond-impregnated cutting tools containfibers. Any known fiber, or combination of fibers, may be added to thecutting tool. In some embodiments, the cutting portion of adiamond-impregnated cutting tool may include fibers such as carbonfibers, metal fibers (e.g., fibers made of tungsten, tungsten carbide,iron, molybdenum, cobalt, or combinations thereof), glass fibers,polymeric fibers (e.g., fibers made of Kevlar), ceramic fibers (e.g.,fibers made of silicon carbide), coated fibers, and/or the like.

In some embodiments, the cutting portion of a diamond-impregnatedcutting tool may contain any carbon fibers. Any known type of carbonfiber may be included in the cutting portion of a diamond-impregnatedcutting tool.

In some embodiments, the fibers may optionally be coated with one ormore additional material(s) before being included in the cutting tool.Such coatings may be used for any performance-enhancing purpose. Forexample, a fiber coating may be used to help retain fibers in thecutting tool. In another example, a fiber coating may be used toincrease lubricity near the cutting face of a cutting tool as the fibercoating erodes away and forms a fine particulate material that acts toreduce friction. In yet another example, a fiber coating may act as anabrasive material and thereby be used to aid in the cutting process.

Any known material may be used to coat the type of fiber(s) that is usedin the cutting tool. For example, any desired metal, ceramic, polymer,glass, sizing, wetting agent, flux, or other substance could be used tocoat a desired type of fiber(s) that may be included in a cutting tool.In one example, carbon fibers could be coated with a metal, such asiron, titanium, nickel, copper, molybdenum, lead, tungsten, aluminum,chromium, or combinations thereof. In another example, carbon fibers maybe coated with a ceramic material, such as SiC, SiO, SiO2, or the like.

Where fibers are coated with one or more coatings, the coating materialmay cover any portion of the fibers and may be of any desired thickness.Accordingly, a coating material may be applied to the fibers in anymanner known in the art. For example, the coating may be applied tofibers through spraying, brushing, electroplating, immersion, vapordeposition, or chemical vapor deposition.

The fibers in the cutting portion of a diamond-impregnated cutting tool,such as a core sampling drill bit, may be of any size or combination ofsizes, including mixtures of different sizes. For instance, fibers maybe of any length and have any desired diameter. In some embodiments, thefibers may be approximately 10 to about 25,000 microns long and may havea diameter of approximately 1 to about 500 microns. In otherembodiments, the fibers may be approximately 150 microns in length andmay have a diameter of approximately 7 microns.

The fibers may be of any shape or combination of shapes. The fibers maybe ribbon-like, cylindrical, polygonal, elliptical, straight, curved,curly, coiled, bent at angles, etc. For instance, FIG. 2 illustratesthat in some embodiments, the majority of the fibers 6 may be curved. Inother embodiments, such as when the cutting tool comprises a coresampling drill bit, the fibers have a substantially cylindrical shape.

Additionally, the fibers may also be of any type or combination oftypes. Examples of the types of fibers include chopped, milled, braided,woven, grouped and wound, or tows. In some embodiments, such as when thecutting tool comprises a core sampling drill bit, the fibers can containa mixture of chopped and milled fibers. In some embodiments, adiamond-impregnated cutting tool contains one type of fiber. In otherembodiments, though, the cutting tool may contain multiple types offibers. In such instances, where a cutting tool contains more than onetype of fiber, any combination of fiber type, quality, size, shape,grade, coating, and/or fiber with any other characteristic may be used.

The fibers may be found in any desired concentration in the cuttingtool. For instance, the cutting portion of a cutting tool may have avery high concentration of fibers, a very low concentration of fibers,or any concentration in between. In some embodiments, the cutting toolmay contain fibers ranging from about 0.1 to about 70 vol %. In otherembodiments, the cutting tool may contain fibers ranging from about 0.1to about 30 vol %. A first portion of the cutting tool may have a firstconcentration of a particular type of reinforcing fiber and anotherportion may have a different concentration (either lower or higher) ofthe same or another type of reinforcing fiber.

In some embodiments, fibers may be homogenously dispersed throughout thecutting portion of a cutting tool. In other embodiments, though, theconcentration of fibers may vary throughout any desired portion of acutting tool, as desired. Indeed, any desired variation of theconcentration of fibers may be implemented in a cutting tool. Forexample, where the cutting tool comprises a core sampling drill bit, itmay contain a gradient of fibers. In this example, the portion of thematrix layer that is closest to the cutting face of the drill bit maycontain a first concentration of fibers and the concentration of fiberscould gradually decrease or increase towards the backing layer. Such adrill bit may be used to drill a formation that begins with a soft,abrasive, unconsolidated formation, which gradually shifts to a hard,non-consolidated formation. Thus, the dispersal of the fibers in thedrill bit can be customized to the desired earth formation through whichit will be drilling.

The fiber concentration may also vary in any desired manner in thecutting tool. In other words, a cutting tool may comprise sections,strips, spots, rings, or any other formation that contains a differentconcentration or mixture of fiber reinforcements than other parts of thecutting tool. For example, the cutting portion of a drill bit maycomprise multiple layers, rings, or segments of matrix layer containingfibers. Each ring, layer, or segment of the drill bit may have a roughlyhomogenous (or heterogeneous) concentration of fibers throughout theentire ring, layer or segment. Yet the concentration of fibers may varyfrom ring to ring (or from segment to segment, etc. . . . ). And thevarious rings of differing fiber gradients may be arranged in any order,may contain different fibers or combinations of fibers, and may be ofany desired thickness. In another example, the outer and inner surfacesof a drill bit could be provided with a different concentration offibers than the inner parts of the drill bit.

The fibers may be located in the cutting portion of a cutting tool inany desired orientation or alignment. In some embodiments, the fibersmay run roughly parallel to each other in any desired direction.However, FIGS. 2 and 4 illustrate that, in other embodiments, the fibersmay be randomly configured and may thereby be oriented in practicallyany and/or every direction.

The diamond-impregnated cutting tools with fibers can be made using anyknown method that provides them with the features described above. Forexample, the drill bit described above can be made in the followingexemplary manner. In this example, the first section of the drill bitcan be made with any known method. The fibers can be incorporated intothe drill bit using any method that provides the desired fibers in thedesired location with the desired concentration. For instance, thefibers may be mixed in with the powdered metal that is used to make thecrown of the drill bit. This mixture may then be sintered and/orinfiltrated with a binder. In other embodiments, though, the fibers maybe incorporated by just placing them into the mold that is used to makethe crown of the drill bit. The first section of the drill bit can thenbe connected to the second section using any method known in the art.For example, the first section may be present in the mold that is usedto form the second section of the drill bit and the two ends of the bodymay be fused together. Alternatively, the first and second sections canbe mated in a secondary process such as by brazing, welding, or adhesivebonding.

The diamond-impregnated cutting tools with fibers may be used for anypurpose known in the art, which depends on the type of cutting tool. Forexample, a diamond-impregnated core sampling drill bit may be attachedto the end of a drill string, which is in turn connected to a drillingrig. As the drill string and therefore the drill bit is rotated andpushed by the drill bit, it grinds away the materials in thesubterranean formations that are being drilled. The core samples thatare drilled away are withdrawn from the drill string. The cuttingportion of the drill bit will erode over time because of the grindingaction. This process may continue until the cutting portion of a drillbit has been consumed and the drilling string need be tripped out of theborehole and the drill bit replaced.

The described fibers give diamond-impregnated cutting tools severaladded advantages when compared to conventional cutting tools that lackfibers. First, the addition of the fibers can control the tensilestrength and the erosion rate of the cutting tool, whether to strengthenor weaken these properties. Without being restricted to thisunderstanding, it is believed that the presence of the fibers can be useto modify the amount of voids in the cutting portion of the tools. Andsince the tensile strength and erosion rate depend on the amount ofvoids, modifying the amount of the fibers can be used to tailor thetensile strength and the erosion rate to the amount needed for theparticular end use of the cutting tool. This increased tensile strengthcan also increase the life of a cutting tool, allowing the cuttingportion of the tools to wear at a desired pace and improving the rate atwhich the tool cuts.

Second, the addition of fibers may also weaken the structure of thecutting portion and allow higher modulus binders to be used for thecutting tools, but at a lower cost. Thus, the amount of fibers in thecutting portion can be tailored to retain the diamonds in the cuttingportion for the desired length of time.

A third advantage is that the fibers may also act as abrasive cuttingmedia that aid in the cutting process. A fourth advantage is that as thefibers in the cutting portion erode away, their fine particulate mattercan reduce friction and increase the lubrication at the interfacebetween the cutting portion and the surface being cut, allowing easiercutting and better flushing. This increased lubrication may also reducethe amount of cutting lubricants (such as drilling muds, polymers,bentonites, etc. . . . ) that are needed, reducing the costs as well asthe environmental impact that can be associated with usingdiamond-impregnated cutting tools.

EXAMPLE

In one example of a comparison between a conventionaldiamond-impregnated cutting tool (one lacking fibers) and afiber-containing diamond-impregnated cutting tool, two sets ofsubstantially similar drill bits were manufactured. In this comparison,the first set of drill bits contained no fibers and the second set wasreinforced with carbon fibers. Each drill bit was then tested and thefollowing properties were measured.

Penetration Rate The average penetration rates of the first set of drillbits ranged from about 30 to about 40 meters per shift. Nevertheless,with the second set of fiber-reinforced bits, the drillers consistentlyachieved about 50 meters per shift. This equates to an increase inpenetration rate of about 25% to about 67%.

Bit life: The average bit life of the first set of drill bits was 64meters. Conversely, the average bit life of the second set of drill bitswas about 104 meters. This equates to an increase in bit life of about60%.

In addition to any previously indicated modification, numerous othervariations and alternative arrangements may be devised by those skilledin the art without departing from the spirit and scope of the abovedescription, and appended claims are intended to cover suchmodifications and arrangements. Thus, while the information describedabove with particularity and detail in connection with what is presentlydeemed to be the most practical and exemplary embodiments, it will beapparent to those of ordinary skill in the art that numerousmodifications, including, but not limited to, form, function, manner ofoperation and use may be made without departing from the principles andconcepts set forth herein. Also, as used herein, examples andembodiments are meant to be illustrative only and should not beconstrued as limiting in any manner.

We claim:
 1. A cutting tool including a cutting section comprising: amatrix of one or more of tungsten carbide, tungsten, iron, cobalt, ormolybdenum; a plurality of cutting media dispersed within said matrix;and a plurality of fibers dispersed within said matrix, wherein fibersof said plurality of fibers are about 10 to about 25,000 microns longand have a diameter ranging from about 1 to about 500 microns.
 2. Thecutting tool of claim 1, wherein said plurality of fibers is unorganizedwithin said matrix.
 3. The cutting tool of claim 1, wherein saidplurality of fibers comprises carbon fibers.
 4. The cutting tool ofclaim 1, wherein the cutting tool comprises a drill bit.
 5. The cuttingtool of claim 4, wherein the cutting tool comprises a core samplingdrill bit.
 6. The cutting tool of claim 1, wherein said plurality offibers is coated with carbon, metal, glass, ceramic, or combinationsthereof.
 7. The cutting tool of claim 1, wherein said plurality offibers comprises chopped or milled fibers.
 8. The cutting tool of claim1, wherein said plurality of cutting media comprises diamond crystals.9. The cutting tool of claim 1, wherein the concentration of saidplurality of fibers in said cutting tool ranges from about 0.1 volume %to about 70 volume %.
 10. The cutting tool of claim 9, wherein theconcentration of said plurality of fibers in said cutting tool rangesfrom about 0.1 volume % to about 30 volume %.
 11. A core drill bit,comprising: a shank portion having a first end for attaching to a drillstring component, an opposing second end, and a central axistherethrough, said shank portion defining an interior space about saidcentral axis for receiving a core sample; and an annular cutting portionhaving a first end and an opposing second end, said first end of saidannular cutting portion being secured to and extending away from saidsecond end of said shank portion, said second end of said annularcutting portion comprising a cutting face; wherein said annular cuttingportion comprises a matrix including a plurality of fibers and a hardparticulate material, wherein said hard particulate material includesone or more of tungsten carbide, tungsten, iron, cobalt, or molybdenum;wherein said plurality of fibers comprises fibers having a length todiameter ratio between about 10 to 1 and about 50 to 1 and a diameterbetween about 1 micron and about 500 microns.
 12. The core drill bit ofclaim 11, wherein said plurality of fibers has an unorganizedarrangement within said matrix.
 13. The core drill bit of claim 11,wherein said plurality of fibers comprises carbon fiber.
 14. The coredrill bit of claim 11, wherein said annular cutting portion comprises: afirst cutting section defined by said cutting face and extending towardsaid shank portion a first distance, said first cutting sectioncontaining a first concentration of fibers dispersed throughout saidmatrix thereby providing said first cutting section with a first erosionrate; and a second cutting section extending from said first distancetoward said shank portion, said second cutting section containing asecond concentration of fibers dispersed throughout said matrix therebyproviding said second cutting section with a second erosion rate that isdifferent from said first erosion rate.
 15. A drill bit, comprising: ashank adapted to be secured to a drill string; and a cutting sectionhaving a cutting face, said cutting section extending from said shank,wherein said cutting section comprises: a matrix of one or more oftungsten carbide, tungsten, iron, cobalt, or molybdenum, and a pluralityof unorganized fibers dispersed within said matrix, wherein saidplurality of fibers comprises from about 0.1% to about 30% volume ofsaid cutting section so as to weaken said cutting segment and therebyincrease the erosion rate of said matrix.
 16. The drill bit of claim 15,wherein said plurality of fibers is adapted to increase the lubricity atsaid cutting face as said matrix erodes.
 17. The drill bit of claim 15,further comprising a plurality of diamond cutting media impregnatedwithin said matrix.
 18. The drill bit of claim 15, wherein said cuttingportion further comprises: a first portion containing a firstconcentration of fibers thereby providing said first portion with afirst erosion rate; and a second portion containing a secondconcentration of fibers thereby providing said second portion with asecond erosion rate that is different from said first erosion rate. 19.A drill bit, comprising: a shank adapted to be secured to a drillstring; and a cutting section having a cutting face, said cuttingsection extending from said shank, wherein said cutting sectioncomprises: a matrix of hard particulate material comprising one or moreof tungsten carbide, tungsten, iron, cobalt, or molybdenum, and aplurality of unorganized fibers dispersed within said matrix, whereinsaid plurality of fibers comprises fibers having a length to diameterratio between about 10 to 1 and about 50 to 1 to weaken said cuttingsection thereby increasing the erosion rate of said cutting section. 20.The drill bit as recited in claim 19, wherein said plurality of fiberscomprise carbon fibers.
 21. The drill bit as recited in claim 20,wherein fibers of said plurality of fibers have a length of about 10microns to about 25,000 microns and a diameter from about 1 micron toabout 500 microns.
 22. The drill bit of claim 15, wherein fibers of saidplurality of fibers have a length of about 10 microns to about 25,000microns and a diameter from about 1 micron to about 500 microns.